Induction of capacitation on boar sperm for a novel relaxin-like protein and its signaling pathway

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This research project was planned to elucidate the physiological significance of relaxin-like protein(RLP) during sperm capacitation. In detail, I will 1) determine whether RLP actually induces boar sperm capacitation and acrosome reaction in vitro, and 2) clarify the intracellular signaling pathways involved in the regulation of RLP-induced capacitation and the acrosome reaction. The outcome of this research is as follows.1.Induction of boar sperm capacitation and acrosome reaction by RLPWhen assessed by Chlortetracycline (CTC) analysis, seminal RLP induced sperm capacitation and acrosome reaction in a dose dependent manner, and the percentage of capacitated sperm was much higher and reached a maximum level (60%) when 150 μg/ml RLP was used. Furthermore, RLP-treated sperm enough high level to fertilizing ability, as assessed by in vitro fertilization test.2.Intracellular signaling pathways involved in the regulation of RLP-induced capacitation and the acrosome reactionWhen investigated the effects of various modulators on boar sperm capacitation, cAMP level and protein tyrosine kinase (PTK) activity induced by RLP, RLP facilitated the influx of HCO_3^-through cholesterol efflux from boar sperm membrane. Also, RLP elevated the cAMP level and PTK activity in the sperm. Thus, the present data suggest that RLP promotes sperm capacitation process via adenylyl cyclase-cAMP-PKA-PTK pathway by facilitation HCO_3^-influx through cholesterol efflux from the sperm membrane.